Depends on your subspecialty, some are busier than others.
There are very few emergencies in general ophthalmology. I come into the office once every 2-3 weekends, but I have a very low threshold for bringing patients in after-hours/weekends. Almost all the stuff I see could probably have waited until Monday. It's not like residency, unless you are covering call for a level 1 trauma center.
If you are starting solo, I'd imagine that call would be nonexistent since you won't have many patients. Then again, you may want to take weekend/ER call to generate patient volume.
I think most solo docs befriend another group/solo doc to cover call while on vacation. The favor is returned in kind. But, the amount of cooperation will vary widely, depending on the competitive nature between groups. I'm going to generalize but smaller towns tend to have shared call. Some medium sized cities will have a local ophthalmology society - the practices in the society can opt into a shared weekend/holiday call.
